KR20210083968A - Display device - Google Patents

Abstract

A display device includes: a display panel connected to a data line, a sensing line and a gate line, including a light emitting element and a driving element for controlling a current flowing through the light emitting element, and disposed therein with a plurality of pixels; a data driving circuit that supplies a data voltage and a reference voltage to the pixel through the data line and the sensing line, respectively, and senses a sensing voltage through the sensing line, so as to output sensed data; a gate driving circuit for supplying a scan signal in synchronization with the data voltage through the gate line; and a timing controller that controls the data driving circuit and the gate driving circuit to output input image data through the display panel to change the data voltage using the sensed data. The timing controller controls the data driving circuit and the gate driving circuit to supply a reference voltage to the first electrode of the driving element connected to the light emitting element through the sensing line while the driving element is turned off, and senses, upon every first time, a potential of the sensing line connected to the first electrode is sensed as the first sensing voltage, thereby obtaining first sensed data.

Description

display device {DISPLAY DEVICE}

This specification relates to a display device, and more particularly, to a display device for detecting a minute short circuit of an OLED.

The flat panel display includes a liquid crystal display (LCD), an electroluminescence display, a field emission display (FED), a quantum dot display panel (QD), and the like. . The electroluminescent display is divided into an inorganic light emitting display and an organic light emitting display according to the material of the light emitting layer. Pixels of the organic light emitting diode display include organic light emitting diodes (OLEDs), which are light emitting devices that emit light by themselves, and emit light to display an image.

An active matrix type organic light emitting display panel including an OLED has an advantage in that a response speed is fast and luminous efficiency, luminance, and a viewing angle are large.

In an organic light emitting display device, pixels including an OLED and a driving transistor are arranged in a matrix form, and the luminance of an image implemented in the pixel is adjusted according to a gray level of video data. The driving transistor controls the driving current flowing through the OLED according to the voltage applied between its gate electrode and the source electrode. The amount of light emitted by the OLED is determined according to the driving current, and the brightness of the image is determined according to the amount of light emitted by the OLED.

A process of manufacturing a display panel includes a deposition process and a repair process. The deposition process is a process in which a conductive layer, a metal layer, an insulating layer, etc. are deposited on a substrate to form a structure such as a device including an electrode, a power line, a signal line, etc. It is a process of darkening existing sub-pixels.

Defects that occur in the display panel manufacturing process can be repaired through the repair process, but progressive defects, in which small foreign substances introduced in the display panel manufacturing process combine with structurally weak parts, and the defect progresses gradually, are hard to find

The embodiments disclosed in this specification take this situation into account, and an object of this specification is to provide a method of detecting a defect in a pixel included in a display panel.

A specific object of this specification is to provide a method for detecting a micro-short circuit between an anode and a cathode of an OLED included in a pixel.

According to an exemplary embodiment, a display device includes: a display panel connected to a data line, a sensing line, and a gate line, the display panel including a light emitting device and a driving device for controlling a current flowing through the light emitting device, the display panel having a plurality of pixels; a data driving circuit for supplying a data voltage and a reference voltage to a pixel through a data line and a sensing line, respectively, and sensing the sensing voltage through a sensing line to output sensed data; a gate driving circuit for supplying a scan signal in synchronization with the data voltage through the gate line; and a timing controller configured to control the data driving circuit and the gate driving circuit to output input image data through the display panel and to change the data voltage by using the sensed data.

The timing controller controls the data driving circuit and the gate driving circuit to supply a reference voltage to the first electrode of the driving device connected to the light emitting device in a state in which the driving device is turned off, through a sensing line, and a first time elapses It is characterized in that the first sensing data is obtained by sensing the potential of the sensing line connected to the first electrode as the first sensing voltage.

According to another exemplary embodiment, in a method for sensing a characteristic of a pixel included in a display device, a black data voltage is supplied to a data line to turn off the driving device connected to the light emitting device included in the pixel, and the first supplying a reference voltage through a sensing line connected to the electrode; and outputting the potential of the sensing line connected to the first electrode as the first sensing data when a first time elapses after stopping the supply of the reference voltage to the first electrode.

When sensing the characteristics of a pixel using an external compensation method, it is possible to distinguish the shift of the threshold voltage of the driving transistor and the anode-cathode short of the OLED from each other. In addition, it is possible to detect a progressive defect occurring after the display panel is shipped, so that the pixel in which the defect is detected can be compensated. Accordingly, the defective pixel is not conspicuous, thereby increasing user satisfaction.

1 is a diagram illustrating a connection between an external compensation circuit sensing the characteristics of a sub-pixel and a sub-pixel;
2 is a diagram illustrating timing of signals related to sensing a threshold voltage of a driving transistor included in a sub-pixel;
3 shows the sensing data level of the external compensation circuit, which is the basis for determining the bad pixel,
4 illustrates a situation in which the source electrode of the driving transistor floats when a short circuit does not occur in the OLED included in the sub-pixel;
5 shows a situation in which a current path occurs when a minute short circuit occurs between the anode and the cathode of the OLED included in the sub-pixel;
6 shows a control signal and sensing voltage for sensing the anode-cathode short circuit of the OLED,
7 is a functional block diagram illustrating an organic light emitting diode display sensing a short circuit of an OLED.

Hereinafter, preferred embodiments will be described in detail with reference to the accompanying drawings.

Like reference numerals refer to substantially identical elements throughout. In the following description, if it is determined that a detailed description of a known function or configuration related to the contents of this specification may unnecessarily obscure or obstruct the understanding of the contents, the detailed description thereof will be omitted.

The external compensation operation for sensing the characteristic of a pixel may be performed in a vertical blank section during an image display operation, during a power-on sequence before image display starts, or during a power-off sequence after image display is finished. The vertical blank period is a period in which a data voltage for image display is not written to a pixel, and is disposed between vertical active periods in which a data signal of one frame is written. The power-on sequence refers to an operation performed from when the power is turned on to display an image to drive the device, and the power-off sequence is performed from the end of the image display until the power is turned off. means action.

In this external compensation operation, a voltage stored in a capacitor of a sensing line (a source node voltage of the driving transistor) is sensed after the driving transistor is operated in a source follower method. External compensation senses the voltage of the source node when the source node potential of the driving transistor is saturated, that is, when the drain-source current (Ids) of the driving transistor becomes zero in order to compensate the threshold voltage deviation of the driving transistor. .

Hereinafter, a pixel may refer to a sub-pixel in some cases.

FIG. 1 illustrates a connection between an external compensation circuit sensing characteristics of a sub-pixel and a sub-pixel, and FIG. 2 illustrates timing of signals related to sensing a threshold voltage of a driving transistor included in the sub-pixel.

The sub-pixel SP to which the external compensation is applied includes a driving transistor DT as a driving element, an organic light emitting diode OLED as a light emitting element, a storage capacitor Cst, a first switching transistor ST1, and a second switching transistor ST2 as a light emitting element. ) may be included. Although the subpixel of FIG. 1 has a 3T1C structure, it may be configured as 3T2C, 4T2C, 5T1C, 6T2C, or the like when a compensation circuit is added.

Transistors constituting the sub-pixel SP may be implemented as a p-type, an n-type, or a hybrid type in which a p-type and an n-type are mixed. In addition, the semiconductor layer of the transistors constituting the subpixel SP may include amorphous silicon, polysilicon, or oxide.

OLEDs emit light according to the pixel current generated by the driving transistor. The OLED includes an anode electrode connected to the second node N2 , a cathode electrode connected to an input terminal of the low potential power supply voltage EVSS, and an organic compound layer positioned between the anode electrode and the cathode electrode.

The driving transistor DT controls the pixel current input to the OLED according to the gate-source voltage Vgs. The driving transistor DT has a gate electrode connected to a first node N1 , one of the first electrode and the second electrode connected to an input terminal of the high potential power supply voltage EVDD, and the other one connected to the second node N2 . ), and the source electrode of the driving transistor DT may be connected to the second node N2 .

The storage capacitor Cst is connected between the first node N1 and the second node N2 .

The first switching transistor ST1 applies the data voltage Vdata supplied to the data line 14A through the DAC to the first node N1 in response to the scan signal SCAN. The data voltage Vdata is a voltage corresponding to input image data when the display is driven, and the sensing data voltage Vdata that turns on the driving transistor DT and turns off the driving transistor DT when the sense is driven. It may be a black data voltage Vblack.

In the first switching transistor ST1 , a gate electrode is connected to the first gate line 15A, one of the first electrode and the second electrode is connected to the data line 14A and the other is connected to the first node N1 . is connected to

The second switching transistor ST2 switches a current flow between the second node N2 and the sensing line 14B in response to the sense signal SENS. The second switching transistor ST2 has a gate electrode connected to the second gate line 15B, one of the first electrode and the second electrode connected to the sensing line 14B, and the other one connected to the second node N2. is connected to

The scan signal SCAN and the sense signal SENS may have different operation timings or the same operation timings. When the operation timings are the same, the first and second switching transistors ST1 and ST2 may have the same gate line. (15) can be connected.

The sensing unit sensing the characteristic of the sub-pixel supplies the reference voltage Vref to the sensing line 14B, detects the voltage of the second node N2 through the sensing line 14B, and outputs the sensing data SD. As a configuration for this, it may be included in the data driving circuit.

The sensing unit supplies the reference voltage Vref to the analog-to-digital converter ADC for converting the voltage of the second node N2 charged in the sensing line 14B into sensing data SD and the sensing line 14B. It may be configured to include a sensing unit including a first switch (SW1) and a second switch (SW2) for connecting the sensing line (14B) to the ADC.

A sensing unit may be provided for each sensing line 14B, and the ADC may be connected to a plurality of sensing units one by one.

A parasitic sensing line capacitor Csl may be provided on the sensing line 14B to store the voltage of the second node N2 or the reference voltage Vref.

The first switch SW1 operates in response to the charging control signal PRE, and the second switch SW2 operates in response to the sampling control signal SAM.

The sensing data SD is data including the characteristics of the sub-pixel SP, that is, the characteristics of the driving transistor included in the sub-pixel SP and the characteristics of the OLED, and is data supplied to the sub-pixels by the timing controller based on the data. It may be supplied to a timing controller to generate a compensation value for compensating for the voltage.

The sensing operation for sensing the characteristic of the sub-pixel SP through an external compensation method includes a first period t1 for initializing the sub-pixel, a second period t2 for sensing the threshold voltage of the driving transistor DT, and the driving transistor It may be configured as a third period t3 corresponding to a conversion period for turning off DT and proceeding to the next stage.

In FIG. 2 , the scan signal SCAN and the sense signal SENS are synchronized and operated at the same timing.

At the beginning of the first period t1 , the sensing data voltage Vdata for turning on the driving transistor DT is supplied to the data line 14A, and the scan signal SCAN is turned on at the turn-off level. level, the first and second switching transistors ST1 and ST2 are turned on, and the first node N1, which is the gate electrode of the driving transistor DT, becomes the sensing data voltage Vdata, and the driving transistor ( DT) is turned on.

In the middle of the first period t1, the charge control signal PRE is changed from the turn-off level to the turn-on level, the first switch SW1 is turned on, and the sensing line 14B is connected to the reference voltage Vref. is charged, and the second node N2 serving as the source electrode of the driving transistor DT becomes the reference voltage Vref through the second switching transistor ST2 in the turned-on state.

In the second period t2, the data voltage Vdata for sensing to turn on the driving transistor DT is continuously supplied to the data line 14A, and the charge control signal PRE is turned on at the turn-on level. The reference voltage Vref is not supplied to the sensing line 14B by changing to the off level. Instead, as a current flows through the driving transistor DT in the turned-on state, the potential of the second node N2 rises from the reference voltage Vref, and the potential of the second node N2 is the gate electrode of the first node ( It increases until the voltage Vdata-Vth is lower than the sensing data voltage Vdata of N1 by the threshold voltage Vth of the driving transistor DT.

When the second period t2 ends or the third period t3 begins, the sampling control signal SAM is turned on for a short time, and the voltage Vsen stored in the capacitor Csl of the sensing line 14B, that is, (Vdata-Vth) is supplied to the ADC and the ADC converts it into sensing data (SD). Since the sensing data SD outputs data reflecting the threshold voltage Vth of the driving transistor DT, the timing controller may compensate the data voltage of the image data to be supplied to the corresponding sub-pixel based on this.

In the third period t3 , a black data voltage Vblack for turning off the driving transistor DT is supplied to the data line 14A, and the first node N1 is changed to a black data voltage Vblack, and the driving transistor (DT) is turned off. Also, the scan signal SCAN is changed to a turn-off level in the middle of the third period t3 , and the second node N2 is in a floating state to maintain the voltage in the second period t2 as it is.

3 illustrates an output data level of an external compensation circuit as a basis for determining a bad pixel.

As shown in FIG. 2 , in the second period t2 for sensing the threshold voltage of the driving transistor DT, the driving transistor DT is turned on, and accordingly, a current flows and the voltage of the second node N2 rises. It increases to a value obtained by subtracting the threshold voltage Vth from the sensing data voltage Vdata.

The display device determines whether the corresponding sub-pixel is defective or not, based on the value of the sensing data SD. For example, the sensing data SD output in 10-bit is in the range of 0 to 1023, for example, 50 or less. or more than 700, it is considered a bad pixel. Accordingly, the display device may not turn on the driving transistor by supplying black data Vblack to the corresponding subpixel when the display is driven so that the corresponding subpixel does not emit light. Alternatively, the display device may compensate the data voltage applied to the corresponding sub-pixel with reference to the compensation data of the normal pixel in the vicinity of the corresponding sub-pixel.

On the other hand, when the sensing data SD output in 10-bit outputs a value in a predetermined normal range, for example, 50 and 700, the display device regards it as a normal pixel and operates the display based on the sensing data SD. The corresponding sub-pixel is driven by compensating for the data voltage.

On the other hand, a fine short (or short circuit) may occur between the anode and cathode electrodes of the OLED due to foreign substances or problems occurring in the manufacturing process, and the sensing data (SD) may be affected by the fine short circuit of the OLED and the sensing data The output value of (SD) may increase in a certain range.

However, when the output of the sensing data SD falls within the aforementioned normal range, whether this value fully reflects the change in the threshold voltage Vth of the driving transistor DT, or a micro-short occurs in the OLED and the sensing data ( SD), it is not possible to distinguish whether it contains more influences on the output.

When the data voltage is compensated by reflecting the sensing data SD as it is in a state in which a micro short circuit occurs in the OLED and affects the output of the sensing data SD, the threshold voltage Vth of the driving transistor DT is accurately calculated. It cannot be compensated, and accurate luminance control cannot be performed.

4 shows a situation in which the source electrode of the driving transistor is floated when a short circuit does not occur in the OLED included in the subpixel, and FIG. 5 shows the current when a minute short circuit occurs in the anode and the cathode of the OLED included in the subpixel. It shows the situation in which the path occurs.

When there is no short circuit between the anode electrode and the cathode electrode of a normal OLED, that is, OLED, the second switching transistor ST2 is turned on without turning on the driving transistor DT to set the second node N2 to the reference voltage ( Vref) and left as it is for a predetermined time, the sensing line 14B and the second node N2 maintain the same potential, so that a current path is not formed.

That is, since the driving transistor DT is also turned off and the reference voltage Vref is lower than the low potential power voltage EVSS, the OLED is also turned off, and the second node N2 that is the source electrode of the driving transistor DT. and the sensing line 14B is in a floating state, so that the voltage does not change.

Therefore, as shown in FIG. 4 , when the reference voltage Vref is, for example, 0V, the sensing voltage Vsen of the sensing line 14B remains 0V, which is the initial sensing voltage Vsen_ini, even after a predetermined time has elapsed. keep

When the second switching transistor ST2 is turned on to supply the reference voltage Vref to the second node N2, the first switching transistor operated by the scan signal SCAN synchronized with the sense signal SENS. ST1 is also turned on, and the data voltage of the data line 14A is supplied to the first node N1 that is the gate electrode of the driving transistor DT. At this time, in order to turn off the driving transistor DT, a black data voltage Vblack must be applied to the data line 14A.

On the other hand, as shown in FIG. 5 , there is a minute short circuit between the anode electrode and the cathode electrode of the OLED, for example, the anode electrode and the cathode electrode are connected with a resistance of several tens of MΩ to generate a short current, ) is turned off, a current path is formed from the input terminal of the low potential power supply voltage EVSS higher than the reference voltage Vref through the resistance of the OLED to the second node N2 and the sensing line 14B. Charges are accumulated in the capacitor Csl formed at 14B.

When a predetermined time elapses in this state, the sensing voltage Vsen of the sensing line 14B rises to become greater than the initial sensing voltage Vsen_ini of 0V.

In this way, in a state in which the driving transistor DT is turned off and the source electrode of the driving transistor DT or the anode electrode of the OLED is initialized, the sensing voltage Vsen of the sensing line 14B connected to the source electrode is applied for a predetermined time. By sensing, it can be checked whether the anode electrode and the cathode electrode of the OLED are short-circuited.

Therefore, before sensing the threshold voltage Vth of the driving transistor DT, by sensing the voltage change of the anode electrode of the OLED in a state in which the driving transistor DT is turned off, a minute short circuit between the anode electrode and the cathode electrode of the OLED If the sensing voltage (Vsen) of the sensing line (14B) connected to the anode electrode of the OLED is changed, it is determined that there is a short circuit in the OLED, and the pixel is processed as defective and the sensing voltage (Vsen) of the sensing line (14B) ), it can be determined that the pixel is normal.

6 shows a control signal and a sensing voltage for sensing an anode-cathode short circuit of an OLED.

The sensing operation for sensing the characteristics of the sub-pixel SP, that is, the threshold voltage Vth of the driving transistor DT and whether the OLED is micro-shorted together through an external compensation method, is performed during the first period t1 for initializing the sub-pixel, the OLED A second period t2 for sensing whether or not a short circuit of , a third period t3 for sensing the threshold voltage of the driving transistor DT, and a conversion for turning off the driving transistor DT and proceeding to the next step It may be configured as a fourth period t4 corresponding to the period.

At the beginning of the first period t1 , a black data voltage Vblack for turning off the driving transistor DT is supplied to the data line 14A, and the scan signal SCAN changes from a turn-off level to a turn-on level. , the first and second switching transistors ST1 and ST2 are turned on, and the first node N1, which is the gate electrode of the driving transistor DT, becomes a black data voltage Vblack, and the driving transistor DT is turned on. is turned off.

In the middle of the first period t1, the charge control signal PRE is changed from the turn-off level to the turn-on level, the first switch SW1 is turned on, and the sensing line 14B is connected to the reference voltage Vref. is charged, and the second node N2 serving as the source electrode of the driving transistor DT becomes the reference voltage Vref through the second switching transistor ST2 in the turned-on state.

Since there is no big problem even if the charge control signal PRE and the scan signal SCAN change from the turn-off level to the turn-on level at about the same time, the charge control signal PRE is also turned-on at the beginning of the first period t1. It can be switched to on-level.

In the second period t2 , the black data voltage Vblack for turning off the driving transistor DT is continuously supplied to the data line 14A, and the charge control signal PRE is turned off at the turn-on level. level, so that the reference voltage Vref is not supplied to the sensing line 14B.

Since the reference voltage Vref supplied to the anode electrode of the OLED is lower than the low potential power supply voltage EVSS supplied to the cathode electrode, the normal OLED (Normal OLED) does not turn on and no current flows. In this case, since the sensing line 14B connected through the anode electrode or the second switching transistor ST2 is in a floating state, the potential of the sensing line 14B or the second node N2 is changed during the second period t2. It does not change from the initially set reference voltage (Vref).

However, if there is a micro-short in the OLED and the anode and cathode electrodes are large but not infinity, but are connected with a resistance component of a predetermined value, for example, a resistance of several tens of MΩ (Abnormal OLED), a low potential A current path flowing to the anode electrode is formed.

In this case, charges are accumulated in the sensing line capacitor Csl of the sensing line 14B connected to the anode electrode of the OLED through the second switching transistor ST2 by the current flowing from the cathode electrode to the anode electrode of the OLED, and the sensing line ( 14B), the sensing voltage Vsen increases.

In the second half of the second period t2, the sampling control signal SAM is briefly turned on to supply the sensing voltage Vsen stored in the capacitor Csl of the sensing line 14B to the ADC, and the ADC transmits it to the OLED. It is converted into sensing data (SD).

At this time, if the sensing voltage Vsen is equal to the reference voltage Vref, it indicates that no current is supplied to the second node N2, and it means that the anode and cathode electrodes of the OLED are not short-circuited and the OLED is normal.

However, if the sensing voltage Vsen does not equal the reference voltage Vref and rises, it indicates that current is being supplied to the second node N2, and since the driving transistor DT is turned off, it means that current flows from the OLED. do.

That is, the anode electrode and the cathode electrode of the OLED are minutely short-circuited, and current flows from the cathode electrode of the OLED having a higher potential to the anode electrode, and the charge is accumulated in the capacitor Csl of the sensing line 14B, that is, in the OLED. means that a defect has occurred.

The timing controller receiving the sensed data SD sensed in the second period t2 determines that the OLED is normal when the sensed data SD corresponds to 0V, which is the reference voltage Vref, but the sensing data SD is 0V. If it corresponds to a higher value, a short circuit occurs in the OLED and the pixel is judged to be defective. When the display is driven, the pixel can be treated as a bad pixel. For example, the black data voltage (Vblack) is set to prevent the pixel from emitting light. The data voltage to be applied to the corresponding pixel may be compensated using the supplied or compensation data of a neighboring normal pixel.

The sensing line capacitor Csl formed on the sensing line 14B is 300pF, the low potential power supply voltage EVSS is 6.5V, the reference voltage Vref is 0V, and the resistance between the anode and the cathode of the OLED is 10MΩ. When , a current of 6.5V/10MΩ=0.65uA flows in the second node N2 or the sensing line 14B, and the sensing voltage Vsen of the sensing line 14B rises from 0V to 1V, which is the reference voltage Vref. The time it takes to make it is 300pF/0.65uA=462usec.

When the threshold voltage Vth of the driving transistor DT is sensed by the conventional voltage sensing method, the time is only increased by about 1% compared to about 40 msec to charge the sensing line 14B. Therefore, it can be said that the time added for detecting the short circuit defect of the OLED is insignificant.

In the third period t3, a sensing data voltage Vdata for turning on the driving transistor DT is supplied to the data line 14A while the scan signal SCAN is maintained at the turn-on level, The sensing data voltage Vdata is supplied to the gate electrode of the driving transistor DT through the first switching transistor ST1 in the turned-on state, so that the first node N1 becomes the sensing data voltage Vdata and is driven The transistor DT is turned on.

Accordingly, as a current flows in the driving transistor DT, the potential of the second node N2, which is the source electrode, rises. The potential of the second node N2 is the data voltage for sensing of the first node N1, which is the gate electrode. Vdata) is increased until the voltage (Vdata-Vth) is lower than the threshold voltage Vth of the driving transistor DT.

When the third period t3 ends or the fourth period t4 starts, the sampling control signal SAM is briefly turned on again, and the voltage Vsen stored in the capacitor Csl of the sensing line 14B; That is, (Vdata-Vth) is supplied to the ADC and the ADC converts it into sensing data (SD). Since the sensing data SD outputs data reflecting the threshold voltage Vth of the driving transistor DT, the timing controller may compensate the data voltage of the image data to be supplied to the corresponding pixel based on this.

In the fourth period t4 , the black data voltage Vblack for turning off the driving transistor DT is supplied to the data line 14A again, and the first node N1 is changed to the black data voltage Vblack for driving. The transistor DT is turned off. Also, the scan signal SCAN is changed to a turn-off level in the middle of the fourth period t4 so that the second node N becomes a floating state and maintains the voltage in the third period t3 as it is.

In this way, before measuring the threshold voltage Vth of the driving transistor DT, the driving transistor DT is turned off to float the source electrode (or the anode electrode of the OLED) of the driving transistor DT. It is possible to determine whether the OLED is short-circuited by sensing the change in potential.

7 is a functional block diagram illustrating an organic light emitting display device for sensing a short circuit of an OLED.

An organic light emitting diode display implementing an external compensation operation for sensing and compensating a threshold voltage of a driving transistor includes a display panel 10 , a timing controller 11 , a data driving circuit 12 , and a gate driving circuit 13 . can do.

The timing controller 11 , the data driving circuit 12 , and the gate driving circuit 13 of FIG. 7 may be all or partly integrated in the drive IC, and the data driving circuit 12 and the gate driving circuit 13 are merged. Thus, it may be configured as one driving circuit.

On the screen on which the input image is displayed on the display panel 10 , a plurality of data lines 14A, sensing lines 14B, and a row are arranged in a column direction (or a vertical direction or a second direction). A plurality of gate lines 15A and 15B arranged in a direction (or a horizontal direction or a first direction) cross each other, and pixels PXL are arranged in a matrix form in each cross region to form a pixel array.

The gate lines 15A and 15B apply the data voltage Vdata supplied to the data line 14A to the pixel, and apply the reference voltage Vref supplied to the sensing line 14B to the pixel. Characteristics of the pixel A scan signal SCAN and a sense signal SENS for supplying a signal to the data driving circuit 12 through the sensing line 14B are supplied to the pixels. When the scan signal SCAN and the sense signal SENS are synchronized and operated at the same timing, only one gate line 15 may be connected to one pixel.

A unit pixel, which is a standard of resolution, is composed of R subpixels for red color, G subpixels for green color, B subpixels for blue color, and W subpixels for white color, or R subpixels It can consist of pixels, G subpixels and B subpixels.

The display panel 10 includes a first power line EVDD for supplying a high potential power voltage (or a pixel driving voltage) to the pixels PXL and a second power supply line for supplying a low potential power voltage to the pixels PXL. 2 may further include a power supply line (EVSS) and the like. The first/second power lines are connected to a power source not shown. The second power line may be formed in the form of a transparent electrode covering the plurality of pixels PXL.

Touch sensors may be disposed on the pixel array of the display panel 10 . The touch input may be sensed using separate touch sensors or may be sensed through pixels. The touch sensors are on-cell type or add-on type, in-cell type touch disposed on the screen AA of the display panel PXL or embedded in a pixel array. It can be implemented with sensors.

In the pixel array, pixels PXL disposed on the same horizontal line are connected to any one of the data lines 14A and the gate lines 15 to form a pixel line (or a display line).

The pixel PXL is electrically connected to the data line 14A in response to the scan signal SCAN applied through the gate line 15 , receives a data voltage, and emits OLED light with a current corresponding to the data voltage. Among the pixels PXL disposed on the same pixel line, pixels connected to the same gate line 15 simultaneously operate according to a scan signal applied from the corresponding gate line.

The pixel PXL receives a high potential power supply voltage EVDD and a low potential power supply voltage EVSS from a power supply unit (not shown). The pixel PXL may have a circuit structure suitable for sensing the threshold voltage Vth of the driving transistor DT that changes according to the lapse of driving time and/or the panel temperature and/or environmental conditions. The configuration of the pixel PXL circuit may be variously modified. For example, the pixel PXL may include a plurality of switch elements and at least one storage capacitor in addition to a light emitting element and a driving element.

The power supply unit adjusts the DC input voltage provided from the host using a DC-DC converter, so that the gate-on voltage and gate-off required for the operation of the data driving circuit 12 and the gate driving circuit 13 are A voltage and the like are generated, and a high potential power supply voltage EVDD, a low potential power supply voltage EVSS, and a reference voltage Vref required for driving the pixel array are also generated.

The host system may be an application processor (AP) in a mobile device, a wearable device, a virtual/augmented reality device, and the like. Alternatively, the host system may be a main board such as a television system, a set-top box, a navigation system, a personal computer, and a home theater system, but is not limited thereto.

The timing controller 11 may temporally separate the sense driving and the display driving according to a predetermined control sequence. Here, the sense driving is a driving for sensing the threshold voltage of the driving transistor and updating a compensation value accordingly, and the display driving is driving to reproduce an image by writing image data DATA reflecting the compensation value to the display panel 10 . to be.

In addition, the sense driving senses whether the OLED, which is a light emitting element, is short-circuited when sensing the threshold voltage of the driving transistor and outputs the sensing data SD, and the timing controller 11 based on this senses the defect of the OLED included in the pixel. It is determined whether the display is defective, and if it is determined that the display is defective, the pixel may be treated as a defective pixel when the display is driven.

Under the control of the timing controller 11 , the sense driving may be performed in a power-on sequence before display driving starts, a power-off sequence after display driving is finished, or in a vertical blank period between the vertical active periods. The power-on sequence refers to a period during which an operation is performed after the system power is applied until the screen is turned on, and the power-off sequence refers to a period during which an operation is performed after the screen is turned off until the system power is released.

The sense driving may be performed in a state in which only the screen of the display device is turned off while system power is being applied, for example, in a standby mode, a sleep mode, a low power mode, and the like. The timing controller 11 may detect a standby mode, a sleep mode, a low power mode, etc. according to a predetermined detection process, and may control operations necessary for sense driving.

The timing controller 11 supplies the image data DATA transmitted from the host system to the data driving circuit 12 . The timing controller 11 receives timing signals, such as a vertical synchronization signal (Vsync), a horizontal synchronization signal (Hsync), a data enable signal (DE), and a dot clock (DCLK) from the host system, and includes the data driving circuit 12 and Control signals for controlling the operation timing of the gate driving circuit 13 are generated. The control signals include a gate control signal GCS for controlling an operation timing of the gate driving circuit 13 and a data control signal DCS for controlling an operation timing of the data driving circuit 12 .

The timing controller 11 may generate the control signals DCS and GCS for driving the display and the control signals DCS and GCS for driving the sense differently.

The timing controller 11 receives, from the data driving circuit 12, the first sensing data SD1 indicating whether the OLED is short-circuited and the second sensing data SD2 for the threshold voltage of the driving transistor during sense driving, It is determined whether the OLED is shorted based on the first sensing data SD1, and a compensation value capable of compensating for the luminance deviation due to deterioration of the threshold voltage of the driving transistor is calculated based on the second sensing data SD2. It can be stored in a memory (not shown).

The compensation value stored in the memory may be updated whenever the sense operation is repeated, and accordingly, it is possible to easily compensate for the deviation of the threshold voltage characteristic of the driving transistor that changes over time. The timing controller 11 reads a compensation value from the memory when driving the display, corrects the input image data DATA based on the compensation value, and supplies it to the data driving circuit 12 .

When the first sensing data SD1 is input above a predetermined reference value, the timing controller 11 determines that a defect has occurred in the corresponding pixel due to minute short-circuiting between the anode electrode and the cathode electrode of the OLED, and when the display is driven, the corresponding pixel bad pixels can be processed. For example, it is possible to provide black data instead of image data to the pixel so that the pixel does not emit light or compensate the data voltage to be applied to the pixel using compensation data of a neighboring normal pixel. can

The data driving circuit 12 may include at least one source drive IC. The source drive IC includes a plurality of data drivers connected to the data line 14A.

When driving the display, the data driver of the source drive IC samples and latches the digital video data (DATA) input from the timing controller 11 based on the data control signal (DCS) and converts it into parallel data, and the latched digital data is converted into an analog data voltage according to a gamma initialization voltage through a digital-to-analog converter (DAC), and the data voltage is supplied to the pixels through an output channel and data lines 14A. The data voltage may be a value corresponding to the gray level to be expressed by the pixel.

During the sense driving, the data driving unit may generate a sensing data voltage and a black data voltage according to the data control signal DCS and supply the generated data voltage to the data lines 14A.

The sensing data voltage is applied to the gate electrode of the driving transistor, which is the driving element, to turn on the driving transistor (ie, a voltage for setting the pixel current), and the black data voltage is applied to the gate electrode of the driving transistor to drive the driving transistor. This is the voltage that turns the transistor off (ie, the voltage that cuts off the pixel current).

The sensing data voltage and the black data voltage are applied to the sensing target sub-pixel in the order described with reference to FIG. 6 , and the black data voltage is supplied in the first, second, and fourth periods constituting the sense driving period. , a data voltage for sensing is supplied in the third period.

The source drive IC includes a plurality of sensing units connected to the sensing line 14B and a sensing unit including an ADC that converts the sensing voltage sensed by the sensing units into sensing data.

Each sensing unit SU may be connected to the sensing line 14B, and may be selectively connected to the ADC through the second switch SW2. Each sensing unit may be implemented by a current sensing method including a current integrator or a voltage sensing method. The sensing unit of FIG. 1 corresponds to a voltage sensing method. The current sensing method is suitable for low current sensing, but it is sensitive to noise and thus requires repeated sensing. The voltage sensing method is difficult to sense low current but is not sensitive to noise, so there are advantages and disadvantages to each other.

The ADC may convert the sensing voltage Vsen input from each sensing unit into sensing data SD and output it to the timing controller 11 .

The source drive IC provides a charging control signal PRE and a sampling control signal SAM for controlling the operations of the first and second switches SW1 and SW2 of the sensing unit according to the data control signal DCS during the sense driving. 6 can be created and supplied to the sensing unit.

That is, the source drive IC supplies the charge control signal PRE in the form of a pulse of the turn-on level in the first period t1 during the sense driving to turn on the first switch SW1 to turn on the sensing line 14B ) is charged to the reference voltage Vref, and in the second half of the second period t2, the sampling control signal SAM is supplied in the form of a short pulse of a turn-on level to turn on the second switch SW2 for sensing. Allows the ADC to convert the sensing voltage Vsen, which is charged in the line 14B, reflecting whether the OLED is short-circuited or not, into the sensing data SD, and the latter half of the third period t3 or the fourth period t4 Threshold voltage ( ) of the driving transistor DT, which is charged in the sensing line 14B by supplying the sampling control signal SAM in the form of a short pulse of the turn-on level to turn on the second switch SW2 at the beginning of Vth) is reflected and the ADC converts the sensing voltage (Vsen) into sensing data (SD).

The gate driving circuit 13 is a plurality of gate driving integrated circuits each including a shift register, a level shifter for converting an output signal of the shift register to a swing width suitable for driving a transistor included in a pixel, an output buffer, and the like. can be configured. Alternatively, the gate driving circuit 13 may be directly formed on the lower substrate of the display panel 10 using a GIP (Gate Drive IC in Panel) method. In the case of the GIP method, the level shifter may be mounted on a printed circuit board (PCB), and the shift register may be formed on a lower substrate of the display panel 10 . The scan signal swings between the gate-on voltage and the gate-off voltage.

When driving the display, the gate driving circuit 13 generates a display scan signal in a row-sequential manner based on the gate control signal GCS and sequentially provides it to the gate line 15 connected to each pixel line. The display scan signal is supplied to the gate line 15 in synchronization with the supply of the data voltage of the data line 14A.

The gate driving circuit 13 may generate the sensing scan signals SCAN and SENS shown in FIG. 6 based on the gate control signal GCS during sense driving and provide the generated scan signals SCAN and SENS to the gate line 15 . The scan signal for use is supplied at a turn-on level during the first to fourth periods t1 to t4 to turn on the first and second switching transistors ST1 and ST2, and in the second half of the fourth period t4 It is changed to a turn-off level to turn off the first and second switching transistors ST1 and ST2.

During the first to fourth periods t1 to t4 , the first and second switching transistors ST1 and ST2 are turned on so that the first node N1 that is the gate electrode of the driving transistor DT is connected to the data line 14A ) and the second node N2 is connected to the sensing line 14B. During the second period t2 for sensing whether the OLED is short-circuited, the driving transistor DT must be turned off, so the black data voltage Vblack must be supplied to the data line 14A and the driving transistor DT must be turned off. Since the driving transistor DT must be turned on during the third period t3 for sensing the threshold voltage, the sensing data voltage Vdata must be supplied to the data line 14A.

Therefore, in the process of sensing the threshold voltage of the driving transistor included in the pixel using the external compensation method, whether the OLED, which is the light emitting element, is short-circuited is sensed to determine whether the pixel is defective, and the pixel determined to be defective does not emit light or the neighbor is normal. By compensating using pixels, bad pixels can be inconspicuous to the user.

The display device described in the specification may be described as follows.

According to an exemplary embodiment, a display device includes: a display panel connected to a data line, a sensing line, and a gate line, the display panel including a light emitting device and a driving device for controlling a current flowing through the light emitting device, the display panel having a plurality of pixels; a data driving circuit for supplying a data voltage and a reference voltage to a pixel through a data line and a sensing line, respectively, and sensing the sensing voltage through a sensing line to output sensed data; a gate driving circuit for supplying a scan signal in synchronization with the data voltage through the gate line; and a timing controller configured to control the data driving circuit and the gate driving circuit to output input image data through the display panel and to change the data voltage by using the sensed data.

The timing controller controls the data driving circuit and the gate driving circuit to supply a reference voltage to the first electrode of the driving device connected to the light emitting device in a state in which the driving device is turned off, through a sensing line, and a first time elapses It is characterized in that the first sensing data is obtained by sensing the potential of the sensing line connected to the first electrode as the first sensing voltage.

In an embodiment, the timing controller may turn off the driving device by supplying a black data voltage to the gate electrode of the driving device through the data line.

In an embodiment, the timing controller may process the first pixel as a bad pixel when the first sensing data input from the first pixel is equal to or greater than a reference value.

In an embodiment, the timing controller turns on the driving element after sensing the first sensing voltage and when a second time elapses, the timing controller senses the potential of the sensing line connected to the first electrode as the second sensing voltage to obtain the second sensing voltage. 2 Sensing data can be obtained.

In an embodiment, the timing controller may turn on the driving device by supplying a sensing data voltage to the gate electrode of the driving device through a data line.

In an embodiment, the timing controller may compensate the data voltage to be supplied to the first pixel in response to the input image data based on the second sensing data input from the first pixel.

In an embodiment, the pixel includes: a driving element including a second electrode supplied with a high potential power voltage; a first switching transistor operating according to the scan signal to connect the data line and the gate electrode of the driving device; a second switching transistor operating according to the scan signal to connect the sensing line and the first electrode of the driving device; a light emitting device including an anode connected to the first electrode of the driving device and a cathode electrode receiving a low potential power voltage; and a capacitor connecting the gate electrode and the first electrode to the gate electrode.

The data driving circuit includes: a first switch for controlling whether a reference voltage is supplied to the sensing line; an analog-to-digital converter (ADC) for converting the voltage of the sensing line into sensing data and outputting it; and a sensing unit configured to include a second switch for controlling the connection between the sensing line and the ADC.

In an embodiment, the timing controller, in a first period, turns on the first and second switching transistors, supplies a black data voltage to the data line to turn off the driving element, and turns the first switch on- is turned on to supply the reference voltage to the first electrode through the sensing line, and in the second period after the first period, the first switch is turned off, and after the first time has elapsed, the second switch is turned on and the ADC is operated. The first sensing data may be obtained from the first sensing voltage of the sensing line.

In an embodiment, the timing controller turns off the second switch in a third period after the second period, supplies a data voltage for sensing to the data line to turn on the driving element, and after the second time period elapses By turning on the second switch and operating the ADC, second sensing data may be obtained from the second sensing voltage of the sensing line.

In an embodiment, the low-potential power supply voltage may be higher than the reference voltage.

According to another exemplary embodiment, in a method for sensing a characteristic of a pixel included in a display device, a black data voltage is supplied to a data line to turn off the driving device connected to the light emitting device included in the pixel, and the first supplying a reference voltage through a sensing line connected to the electrode; and outputting the potential of the sensing line connected to the first electrode as the first sensing data when a first time elapses after stopping the supply of the reference voltage to the first electrode.

In an embodiment, the method for sensing pixel characteristics may further include outputting a potential of the sensing line as second sensing data in a state in which the driving element is turned on by supplying a sensing data voltage to the data line. can

Those skilled in the art from the above description will be able to see that various changes and modifications are possible without departing from the spirit of the present invention. Accordingly, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification, but should be defined by the claims.

10: display panel 11: timing controller
12: data driving circuit 13: gate driving circuit
14: data line 15: gate line

Claims (12)

a display panel connected to a data line, a sensing line, and a gate line, the display panel including a light emitting device and a driving device controlling a current flowing through the light emitting device, the display panel having a plurality of pixels;
a data driving circuit for supplying a data voltage and a reference voltage to the pixel through the data line and the sensing line, respectively, and sensing the sensing voltage through the sensing line to output sensed data;
a gate driving circuit for supplying a scan signal in synchronization with the data voltage through the gate line; and
a timing controller configured to control the data driving circuit and the gate driving circuit to output input image data through the display panel and to change the data voltage using the sensed data;
The timing controller controls the data driving circuit and the gate driving circuit to supply the reference voltage through the sensing line to a first electrode of a driving device connected to the light emitting device in a state in which the driving device is turned off and obtaining first sensed data by sensing the potential of the sensing line connected to the first electrode as a first sensing voltage when a first time elapses. According to claim 1,
and the timing controller turns off the driving element by supplying a black data voltage to the gate electrode of the driving element through the data line. According to claim 1,
and the timing controller processes the first pixel as a bad pixel when the first sensing data input from the first pixel is equal to or greater than a reference value. According to claim 1,
The timing controller is configured to turn on the driving element after sensing the first sensing voltage and, when a second time elapses, sense the potential of the sensing line connected to the first electrode as a second sensing voltage, 2 A display device, characterized in that it obtains sensing data. 5. The method of claim 4,
and the timing controller supplies a sensing data voltage to the gate electrode of the driving element through the data line to turn on the driving element. 5. The method of claim 4,
and the timing controller compensates for a data voltage to be supplied to the first pixel in response to the input image data based on second sensing data input from the first pixel. 5. The method of claim 1 or 4,
The pixel is
the driving element including a second electrode supplied with a high potential power voltage;
a first switching transistor operating according to the scan signal to connect the data line and a gate electrode of the driving device;
a second switching transistor operating according to the scan signal to connect the sensing line and the first electrode of the driving element;
the light emitting device including an anode electrode connected to the first electrode of the driving device and a cathode electrode receiving a low potential power supply voltage; and
a capacitor connecting the gate electrode and the first electrode to the gate electrode;
The data driving circuit is
a first switch for controlling whether the reference voltage is supplied to the sensing line;
an analog-to-digital converter (ADC) for converting the voltage of the sensing line into sensing data and outputting it; and
and a sensing unit configured to include a second switch for controlling a connection between the sensing line and the ADC. 8. The method of claim 7,
The timing controller is
In a first period, the first and second switching transistors are turned on, the driving element is turned off by supplying a black data voltage to the data line, and the reference voltage is turned on by turning the first switch on. is supplied to the first electrode through the sensing line,
In a second period after the first period, the first switch is turned off, the second switch is turned on after the first time has elapsed, and the ADC is operated to obtain a second value from the first sensing voltage of the sensing line. 1 A display device, characterized in that it obtains sensing data. 9. The method of claim 8,
The timing controller is
In a third period after the second period, the second switch is turned off, the driving element is turned on by supplying a sensing data voltage to the data line, and after the second time has elapsed, the second switch is turned on and the ADC is operated to obtain the second sensing data from the second sensing voltage of the sensing line. 9. The method of claim 8,
and the low-potential power supply voltage is higher than the reference voltage. supplying a reference voltage through a sensing line connected to a first electrode of the driving element in a state in which a driving element connected to a light emitting element included in a pixel is turned off by supplying a black data voltage to the data line; and
and outputting the potential of the sensing line connected to the first electrode as first sensing data when a first time elapses after stopping the supply of the reference voltage to the first electrode. How to sense pixel characteristics. 12. The method of claim 11,
and outputting the potential of the sensing line as second sensing data in a state in which the driving element is turned on by supplying a sensing data voltage to the data line. How to sense a characteristic.

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